Following some feedback and further use of my own big stopper i have changed the layout of my custom designed 10 stop filter exposure chart, as well as producing further copies for different value 10 stoppers, it is vital that you calibrate your big stopper or 10 stop filter before you use it, as manufacturing variations may cause significant timing adjustments. This post contains information on 10 Stop Filter Exposure Charts and how to use them as a guide to getting the right exposure value.
To determine how many stops your filter is you will need a tripod or something to keep your camera very still and a well-lit subject preferably non moving, also away from a window unless it’s very cloudy or no clouds as sun variation (sun going behind cloud during exposure) will cause false readings and exposures. A white wall with continuous light(not from a bulb would be ideal and something like a picture frame with colour so as you can tell by contrast how close you are to the original colour).
The aim of this calibration is to get your “before” and “after” images as close as possible.
Start by setting your camera in AV (aperture priority) mode and taking a picture at your lowest aperture f/4 e.g. and note the time value(shutter speed).
Now set the camera into manual mode and set aperture to same as before now insert your filter and adjust the time value to 10 stops (using the 10 stop sheet you just purchased) also adjust your in camera white balance to 10,000 kelvin or as close to it as possible this helps reduce the blue hue generated by the filter,( if you don’t have a kelvin option on your camera (canon 600d, 550d,1100d etc) shoot in raw mode and adjust the white balance point in Adobe camera raw or Adobe Lightroom) now expose again now compare the 2 images on your pc and see if the 2nd one is darker or brighter than the first, (allowing for the blue hue if you didnt set the kelvin). Now simply go back to the camera and take a few more samples in 3rd stop increments either shorter or longer depending or darker or lighter (shorter if your 10 stop exposure was too bright or longer is your big stopper exposure was too dark) and compare these images to the original until you get a match. The Lee big stopper can be colour cast corrected by manually setting you camera to 10,000 kelvin or as high as your camera can get to that some stop at 8000k if you can neutralise the blue cast then its a simply a question of taking your first unfiltered image of some white card or paper (a4 will do) and just expose and cross reference the colour temperature in raw once you have a colour temperature match that equals a correct exposure time.
At this point i would like to add that i have helped a few people calibrate their 10 stop filters and the ones i have done seem to be closer to the 11 stop area another pattern with this is that the close to 11 stops the higher the kelvin needs to be. my own big stopper is 11 stops and requires 10,500k to colour correct.
Now you have determined what value your 10 Stop filter is, you can head over to the shop and download one of the pocket guides accordingly. Here is a sample of what they look like (please note this sample is not the complete chart. Now including comprehensive exposure chart for little stopper.
NOW FREE (donation optional) you will receive a download with your chosen exposure chart ( 6 stop, 8, 9, 9-1/3, 9-2/3, 10, 10-1/3, 10-2/3, 11stop 12 stop and 13 stop) please note this is a digital download and requires saving and or printing.
Important to know if you are using a big stopper with a circular polariser you may need to add a further 2 stops to compensate hence I have now created the 12 and 13 stop charts.
Blue Cast Correction
Many people are not happy with the blue cast that some big stoppers or 10 stop filters produce, the blue cast will vary depending on light strength, angle to the sun and to a certain extent content of the image.
To remove the blue cast easily simply switch your camera to shoot in raw mode and adjust the white balance point in Photoshop or canon digital photo professional software, if you have a Nikon try View NX2 or what ever software came with your camera.
if your not sure how to use the white balance tool please contact me and i will do my best to help you out.
After playing with my Lee Big stopper which i swear is closer to 11 stops! shooting at 10,000 kelvin or as close to will reduce the blue cast.
like wise just had an email from a reader who says his B&W 10 stop filter corrects at 4200k or (tint +6 (lightroom)). Simply put your camera into manual white balance mode and adjust accordingly. If you shoot raw use colour temperature to colour correct if you only shoot jpeg use tint option.